96 EXPERIMENTS UPON ROOT-CROPS 



receiving farmyard manure, and even on those receiving only a 

 complete artificial manm-e, the crop was maintained in favom^- 

 able seasons. No falling- off was observed wdiich could be 

 attributed to the land having become "sick" through the 

 continuous growth of the same crop, or through the accumula- 

 tion of disease in the soil. 



The essential feature of the root-crops is the large amount 

 of digestible carbohydrate they contain ; in the case of Swedes 

 this consists of glucose, which forms 6 to 7 per cent, of the 

 whole weight of the Swedes, the total dry matter being about 

 11 percent, of the whole. In the mangel there is about 8*5 

 23er cent, of cane sugar, the total dry matter being about 12-5 

 per cent. In potatoes the carbohydrate is starch, of which 

 the tubers contain about 20 per cent., out of a total dry matter 

 content of 25 per cent. 



I. — Experiments upon Mangels, Barn Field, 

 1876-1904. 



The area under experiment amounts to about 8 acres, most 

 of the plots being about one- seventh acre in extent ; the whole 

 produce from each plot is weighed, but the roots only are 

 carted away, the leaves after weighing being spread and 

 ploughed in. 



The field is divided longitudinally into seven strips running 

 the whole length of the field ; each of these strips receives 

 one manure throughout its length ; farmyard manure alone on 

 Stri^D 1, and in combination with superphosj^hate and sulphate 

 of potash on Strip 2, nothing on Strip 8, superphosphate 

 alone on Strip 5, superphosphate and sulphate of potash on 

 Strip 6 ; and complete minerals, including fmther sulphate of 

 magnesia and common salt, on Strip 4. The strips are then 

 subdivided into plots by cross - dressings of nitrogenous 

 manures ; nothing on the O Series, nitrate of soda on 

 Series N, ammonium-salts on Series A, rape cake on 

 Series C, and a combination of ammonium-salts and rape 

 cake on Series AC. Thus, as shown in Table XXXIX., 



